Pre-whirl turbo charger apparatus

ABSTRACT

A prewhirl construction for the compressor of a turbocharger. The periphery of the compressor input opening is provided with a plurality of slanted spin vanes which impart a tangential velocity to air entering the compressor. The air is thus provided with a velocity component similar to the compressor&#39;&#39;s impeller velocity. The input duct to the compressor carries a butterfly valve whose setting controls the amount of air entering through the peripheral spin vanes. The operating surge line is moved so as to increase the flow range of the compressor.

United States Patent Benisek 51 Nov. 25, 1975 PRE-WHIRL TURBO CHARGER APPARATUS [75] Inventor: Edward F. Benisek, Indianapolis,

Ind.

[73] Assignee: Wallace Murray Corporation, New

York, N.Y.

[22] Filed: Mar. 18, 1974 [211 App]. No: 452,369

[52] US. Cl 415/116; 415/151 [51] Int. C1. F01D 5/14 [58] Field of Search ..4I5/147, 148, DIG. I, 116, 415/159,144,145,15I

[56] References Cited UNITED STATES PATENTS 1,517,329 12/1924 Weiss et a1 415/148 2,140,148 12/1938 Whitmore 415/159 2,336,010 12/1943 Gregory 415/159 2,405,282 8/1946 Birmann 415/159 2,690,293 9/1954 Muhlberg 415/116 2,798,658 7/1957 McDona1d.. 415/147 3,672.786 6/1972 Mount 415/147 FOREIGN PATENTS OR APPLICATIONS 1,101,684 3/1961 Germany 415/159 661.498 4/1963 Canada 415/116 343,385 2/1931 United Kingdom. 415/116 1,116,535 2/1956 France 415/116 1,069,415 2/1954 France 415/151 Primary ExaminerI-Ienry F. Raduazo Attorney, Agent, or FirmThomas .1. Greer, .Ir.; Harold L. Stowell [57] ABSTRACT A prewhirl construction for the compressor of a turbocharger. The periphery of the compressor input opening is provided with a plurality of slanted spin vanes which impart a tangential velocity to air entering the compressor. The air is thus provided with a velocity component similar to the compressors impeller velocity. The input duct to the compressor carries a butterfly valve whose setting controls the amount of air entering through the peripheral spin vanes. The operating surge line is moved so as to increase the flow range of the compressor.

2 Claims, 5 Drawing Figures U.S. Patent Nov. 25, 1975 Sheet10f3 3,922,108

US. Patent N0v.25, 1975 Sheet2of3 3,922,108

PRE-WI-IIRL TURBO CHARGER APPARATUS This invention relates to the art of turbochargers and more particularly to an arrangement for prewhirling air which enters the compressor. Turbochargers are widely used on internal combustion engines and particularly on large diesel engines for trucks. In distinction to superchargers which derive their power directly from the crankshaft of the engine, turbochargers are driven by the engine exhaust gases. The exhaust is coupled to a turbine with the turbine in turn connected to the compressor. Ambient air is compressed by the compressor and fed into the input of the engine.

Prewhirl or spin devices have been known for air compressors. Such devices often include a plurality of slanted vanes extending across the mouth of the compressor inlet and thereby impart to the incoming air a whirl component to the air, thereby reducing compressor work at a given compressor speed. Such devices are shown in U.S. Pat. Nos. 2,637,486 to Taylor, and 2,690,293 to Muhlberg, for example. Air prewhirl counter to impeller rotation increases the work done by the compressor, while air prewhirl in the same direction decreases the compressor work. The effect of prewhirl is more fully discussed in ASME Paper No. 63- AI-IGT-55 by Anderson and Shouman published March 1963. As set out in the Anderson et al. paper, varying the amount of prewhirl at constant compressor speed is equivalent to varying compressor speed without prewhirl. As also there noted, prewhirl moves the surge line (stall line) to a lower flow and thus expands the operating range.

It is often desirable to vary the amount of prewhirled air entering the compressor and towards this purpose such vanes have been provided with linkages for simultaneously varying the vane angle. While such constructions have served their intended purpose, they are relatively expensive because several moving parts are required. The present invention departs from such prior art constructions in the use of a plurality of stationary spin vanes which are positioned around the periphery of the compressor inlet. The duct leading into the compressor is provided with a butterfly valve. By adjusting the angular position of the butterfly valve, the amount of air entering the compressor which passes over the spin vanes is varied to thereby vary the amount of prewhirl. In lieu of a structure wherein several vanes must be simultaneously adjusted in order to vary the amount of spin of air entering the compressor, a single valve is employed. This construction also exhibits the utility of moving the surge line and then expanding operating range.

IN THE DRAWINGS FIG. 1 is a cross-sectional view illustrating the prewhirl assembly of this invention.

FIG. 2 is a cross-sectional view of the ring element which carries the slanted vanes.

FIG. 3 is a plan view of the ring of FIG. 2.

FIG. 4 is a plot showing the operation of the device with a 0.410 nozzle gap with the butterfly valve 49 open.

FIG. 5 is a plot similar to that of FIG. 4, but with the butterfly valve fully open.

Referring now to the drawings, the numeral denotes a compressor cover of a conventional turbocharger. The dashed element denoted by the numeral ,2 11 indicates a conventional impeller. The compressor cover 10 includes an annular chamber 12 which receives compressed air, the chamber defined by a hollow torus 14 having an integral inlet portion or mouth 18 provided at its periphery with annular flange 20.

gularly rotatable post 36, the latter being adjustable to any desired angular position by means of lever assembly 38,40. The input end of duct 28v is coupled-to air filter 42, the filter extending radially to meet the input of a second duct 44 whose interior defines a plenum chamber communicating with compressor mouth 18 through spin vanes 24. The axial space between the radially outermost portions of vanes 24 and annular elements 20 and 22 define peripherally disposed air input passages 25 (see FIG. 3) through which air may pass. The passages converge, as nozzles, to an exit area 26.

The operation of the device is as follows. With the vane of butterfly valve 34 angularly positioned so as to provide desired air flow in interior 30 of duct 28, the suction pressure in mouth 18 due to pumping action of impeller rotation results in ambient air passing through filter 42, entering duct 28 and pumping through the compressor. A regulated amount of air enters the compressor through passages 25. Should operating conditions be such that prewhirl is desired to change the surge condition, the butterfly valve vane 34 should be closed somewhat to restrict the flow of air through duct 28. Some air is now drawn in through filter 42, through plenum chamber 46 and into passages 25. As may be most readily visualized by reference to FIG. 3, the air is thus given a tangential component of velocity, in the same direction of rotation as that of impeller 1 1. Other air, as before, also passes through 30 into compressor mouth 18.

In the event that a greater proportion of prewhirled air is desired, the butterfly valve 34 is rotated still further to inhibit passage of air through duct 28, with correspondingly increased amounts of air flowing through passages 25 and nozzle exits 26, and thus spun or prewhirled prior to entering mouth 18. The passages 25 are defined by sheet vanes 24 angularly positioned. In lieu of such vanes, other arrangements for yielding slanting nozzles may be employed, such as drilling or casting apertures in a thickened ring.

Referring now to FIG. 4 of the drawings, the operation of the apparatus is shown with valve disc open 49 degrees with respect to the flow axis 30 of duct 28. The several efficiency curves, for the indicated compressor speeds, are shown with their left portions being joined at the surge or stall line. It will be recalled that operating conditions are unstable to the left of the surge line and accordingly all compressor operation must take place to the right of this line. FIG. 5 is a similar plot, except that the butterfly valve is completely open, there being accordingly a minimum of prewhirl imparted to the air entering compressor mouth 18. It will be seen from a comparison of FIGS. 4 and 5 that (as is known in the art) the effect of positive prewhirl is to move the surge line to the left and the operating range of the device thereby extended.

What is claimed is:

l. A compressor installation for a turbocharger for imparting prewhi rl to air entering the compressor, including,

a. a rotary centrifugal compressor having an impeller and having an elongated input flow duct defining a central intake passage in fluid communication with the intake of the impeller,

b. said flow duct having a rotary pivoted disc valve positioned therewithin to control the amount of air passing through the said duct towards said impeller,

c. a plurality of peripherally disposed passages in said duct which establish fluid communication between the interior and the exterior of the said duct, said passages including means for imparting a tangential 4 velocity to air passing therethrough into the duct interior from the duct exterior,

d. said peripheral openings being axially located in said duct between said rotary pivoted disc valve and said centrifugal impeller,

e. a casing surrounding said duct, one end of said casing being closed and meeting said duct at a region downstream of said peripherally disposed passages to thereby define an enlarged annular plenum chamber closed at one end, the other end of said plenum chamber being open and unrestricted and communicating with ambient air.

2. The apparatus of claim 1 including an air filter in air flow communication with said input flow duct and the open end of said annular plenum chamber,

* l l= l 

1. A compressor installation for a turbocharger for imparting prewhirl to air entering the compressor, including, a. a rotary centrifugal compressor having an impeller and having an elongated input flow duct defining a central intake passage in fluid communication with the intake of the impeller, b. said flow duct having a rotary pivoted disc valve positioned therewithin to control the amount of air passing through the said duct towards said impeller, c. a plurality of peripherally disposed passages in said duct which establish fluid communication between the interior and the exterior of the said duct, said passages including means for imparting a tangential velocity to air passing therethrough into the duct interior from the duct exterior, d. said peripheral openings being axially located in said duct between said rotary pivoted disc valve and said centrifugal impeller, e. a casing surrounding said duct, one end of said casing being closed and meeting said duct at a region downstream of said peripherally disposed passages to thereby define an enlarged annular plenum chamber closed at one end, the other end of said plenum chamber being open and unrestricted and communicating with ambient air.
 2. The apparatus of claim 1 including an air filter in air flow communication with said input flow duct and the open end of said annular plenum chamber. 